1. Field of the Invention:
The present invention relates to an end face grinding apparatus for, e.g., a glass plate.
2. Description of the Prior Art:
In a process of cutting a rectangular, trapezoidal or fan-shape glass plate from a large glass plate and grinding (chamfering, plane grinding, U-shape grinding, polishing or the like) end face of the cut plate, conventionally, an operator manually urges a grinding wheel rotating at high speed against the end face of the cut glass plate. The glass plate is drawn by suction so as to be fixed on a rotating table, and is rotated at a constant low speed. On the other hand, a grinding unit including a drive motor and the grinding wheel is supported by a swing arm which can be horizontally pivoted in a direction of a glass plate end face. The end face grinding operation is performed such that a handle provided to the swing arm is pressed so as to urge the grinding wheel against the end face of the glass plate rotating at low speed.
Therefore, in the conventional grinding process, since a manual operation must be performed, a grinding pressure is not uniform. If a rotating speed of the glass plate is constant, the peripheral speed of the end face is changed in accordance with the contour of the glass plate, resulting in irregular grinding speed and variation in grinding margin. Particularly, when an end face of a complex-shaped glass plate such as a windshield glass of a vehicle is to be uniformly chamfered, a highly skilled technique is required. When the grinding wheel is abruptly urged against the glass end face at the grinding start point, the glass plate may be damaged.
For the purpose of automation, there has been proposed, an apparatus in which a grinding unit is movably mounted on a track frame extending along the radial direction with respect to the center of a glass plate, and the glass plate is ground while moving the grinding wheel along a peripheral surface of the glass plate (Japanese Utility Model Application Laid Open No. 154044/83). However, in such an apparatus, since the moving speed of the grinding wheel is manually adjusted so as to obtain a uniform grinding margin, the above-mentioned drawbacks cannot be fully overcome, and variation in grinding margin cannot be eliminated due to manual operation.
Another grinding apparatus comprising a grinding unit movable along the X-Y axes has been proposed so as to grind a contour end face of a glass plate in accordance with NC data (Japanese patent application Laid Open No. 37040/84). According to the apparatus, a grinding speed of the grinding wheel (contour trace speed) can be set constant irrespective of an outer shape of the glass plate. However, the apparatus becomes as large as an NC machine, resulting in high cost and large insulation area.